1. Field of the Invention
The present invention relates to a method of managing an optical transport network (OTN), and more particularly, to an apparatus and method for detecting and treating errors in an optical transponder connected to an OTN.
2. Description of the Related Art
An explosive growth in the Internet traffic greatly increases network traffic, thereby threatening the capacity of a backbone network. To solve this problem, a technique of extending an optical fiber network using Wavelength Division Multiplexing (WDM) has been introduced.
Conventionally, an optical signal with a single wavelength is transmitted through an optical fiber. However, in WDM, a transmitting side multiplexes and transmits optical signals with different wavelengths through an optical fiber and a receiving side splits the optical signals according to their wavelengths. Accordingly, it is possible to increase the capacity of an optical fiber N times using WDM, without further optical fibers and a repeater.
An optical transponder is installed in a transmitting side of such an optical transmission network so as to convert wavelengths of optical signals input from a Synchronous Digital Hierarchy (SDH) system into different WDM wavelengths. The optical transponder generally names an optical transmitter and an optical receiver that convert an optical signal into an electrical signal and then into an optical signal. In general, an optical transponder includes two optical transceivers that perform transmission of an upward/downward signal.
Development of Dense Wavelength Division Multiplexing (DWDM) increases a data transmission rate per optical channel from 2.5 Gbps to 10 Gbps and very soon to 40 Gbps. An increase in the transmission rate via an optical channel triggers a need for reliable operation of an optical channel. In this connection, a digital wrapper that supports a frame structure of a sublayer of an optical channel, suggested in the ITU-T G.709 recommendation, has been recently developed to improve the reliable operation and optical transmission performance of the optical channel.
The digital wrapper according to the ITU-T G.709 recommendation allows various tributary signals, such as an SDH/Synchronous Optical NETwork (SONET) signal and an Ethernet interface signal, (hereinafter referred to as a “G.709 OTN frame”) to be transmitted through an optical channel, regardless of a frame structure. Also, the digital wrapper performs Operation, Administration, and Maintenance (OAM) of an optical signal during transmission of the optical signal including an overhead for OAM of the optical channel and an overhead for forward error correction (FEC), and improves the performance of signal transmission.
Use of a G.709 frame allows operation of overheads for layers of an Optical Transport Unit (OTU), an Optical Data Unit (ODU), and an Optical Payload Unit (OPU), and a total of eight optical channel sublayers of each of the layers to be independently operated according to a user's need. However, although a total number of optical channel sublayers of the respective layers that can operate increases, it is difficult to prevent the increased sublayers from being weighed with load.
In particular, load is likely to be weighed on an optical channel when an error occurs therein. This is because the respective layers may undergo errors independently, and a number of errors occurred is proportional to that of layers of the optical channel. Accordingly, for more reliable operation of the optical channel, there is a strong need for development of an optical transport system that can immediately inform a user of the occurrence of an error in a layer of the optical channel and effectively treat the error.